Microwave radiometric sensing is a means to realize portable, non-invasive, wireless thermometry in order to detect subsurface core body temperatures. The antennas used in microwave radiometry have special considerations in that they must meet high beam efficiency, low ohmic loss, narrow beam solid angle, and high input matching requirements. The antenna can be regarded as one of the most critical components limiting radiometer system performance as being viable for both treatment and detection in the biomedical realm.
Human body antenna designs should explicitly show that all requirements for successfully sensing have been met. Many antenna designs for human body sensing have been presented that exhibit adequate in-band return loss (≥10 dB), but the radiation characteristics are not always provided. Significant shortcomings in the antenna pattern can be masked if the radiation pattern is not provided. Particularly, the antenna should radiate in the broadside direction toward the body and should not be sensitive to the ambient environment nor other areas outside of the body. It is well documented that unwanted and augmented side lobes occur when surface waves reach the edge of a finite ground plane and radiate into the propagation medium. This surface wave propagation negatively affects both the efficiency and radiation pattern of planar antennas and must be mitigated in order to accurately sense while the antenna is on-body.